Valve

ABSTRACT

The invention relates to a valve, particularly a proportional pressure control valve for controlling fluid flows, comprising a valve housing ( 10 ), which has at least three fluid-conducting connections that, in particular, are provided in the form of a pump connection (P), a use connection (A) and of a tank (T) connection. In order to connect, as desired, the pump connection (T) to the use connection (A) and the use connection (A) to the tank connection (T), a control piston ( 18 ) can be guided in a longitudinally displaceable manner inside the valve housing ( 10 ), and this control piston is provided for establishing a fluid-conducting connection between at least one of the connections (P) and a pilot chamber ( 20 ) of a pilot valve ( 22 ) having a connecting channel ( 24 ). A valve ( 40 ) of the pilot valve ( 22 ) is guided in the pilot chamber ( 20 ) in a longitudinally displaceable manner, whereby the connecting channel ( 24 ) has a throttle in the direction of the pilot chamber ( 20 ) of the pilot valve ( 22 ) with the valve part thereof. In addition, a guiding device ( 38 ), which is oriented toward the pilot chamber ( 20 ) and which is provided for guiding the fluid flow, is provided next to the throttle whereby diverting the fluid flow, which is conveyed inside the connecting channel ( 24 ) and which is flowing toward the valve part ( 40 ), at least partially away from this valve part.

The invention relates to a valve, especially a proportional pressurecontrol valve for controlling fluid flows, having a valve housing whichhas at least three fluid-carrying ports, especially in the form of apump port P, a use port A and a tank port T, within the valve housingfor optional connection of the pump port P to the use port A, and of theuse port A to the tank port T, a control piston being guided so as to bemovable in the longitudinal direction, which control piston is providedwith a connecting channel for producing a fluid-carrying connectionbetween at least one of the ports and the pilot chamber of the pilotvalve, the valve part of the pilot valve being guided so as to bemovable in the longitudinal direction in the pilot chamber, and theconnecting channel having a throttle in the direction of the pilotchamber of the pilot valve with its valve part.

A generic valve of this type in the form of a proportional pressurecontrol valve is disclosed by U.S. Pat. No. 6,286,535 B1. In this knownsolution the pump port P in the axial displacement direction of thecontrol piston within the valve housing discharges into the latter, withthe other two ports in the form of the use port A and the tank port Tdischarging transversely thereto in the radial direction, with thecorresponding displacement position of the control piston into anannulus which on one side adjoins the valve housing and on the otherside adjoins the control piston itself. Furthermore, in the knownsolution there is a damping orifice in the control piston whichpermanently connects a damping chamber between the valve housing and thecontrol piston to the indicated annulus. In this way the transientprocesses of the control piston can be damped as required with stillsimultaneously high dynamics for the overall valve; this is necessarywhen these proportional pressure control valves are used preferably inclutch systems which are used for example to connect two shafts, forexample the shafts of machines with transmission shafts.

Furthermore, in the known solution the connecting channel in thedirection of the pilot chamber of the pilot valve with its valve partwithin the control piston has a throttle which on its side facing awayfrom the pilot chamber is provided with a filter part for filtering outdirt in the fluid stream which otherwise could clog the indicatedthrottle and could block it in this way. The fluid stream which isthrottled in this way travels with high pressure to a sphericallyclosing or valve part of the pilot valve which can be actuated by aconventional magnetic system, especially a proportional magnetic system.In the process the indicated fluid stream is routed unbraked afterpassing through the throttle in the extension of the connecting channelto the spherical valve part which is spring-loaded against the action ofthe magnetic system in its closed position along the valve seat of thepilot chamber. The fluid stream which is routed in this way directly tothe valve part applies very high jet forces to the closing elementdesigned to this end to be spherical; this leads to neutral dynamiceffects on the pilot control and in certain valve states malfunctionsare thus possible. Especially when these valves are being used forhydraulically actuated clutches or the like which are subject toincreased requirements in terms of safety engineering, thesemalfunctions however cannot be tolerated.

In a further development this known generic solution moreoverproportional pressure control valves according to U.S. Pat. No.5,836,335 are known in which the control piston has a means for limitingpressure spikes, as could easily occur for example on the use port A towhich hydraulic clutches can be connected. For this purpose, in onepreferred embodiment of the known valve a spring-loaded return valve isinserted into the control piston and clears the fluid-carrying path at adefinable pressure threshold value between the annulus and a containinggroove which is permanently connected to the tank port.

On the basis of the generic prior art the object of the invention is tofurther improve the known solution while retaining its advantages sothat a valve is devised in which it can be ensured that malfunctions,especially relative to the pilot valve, cannot occur in order to devisea valve which meets high safety requirements for appropriate actuationin order to be able to use this valve especially in hydraulic clutchsystems. This object is achieved by a valve, especially a proportionalpressure control valve, with the features specified in claim 1 in itsentirety.

In that, as specified in the characterizing part of claim 1, in additionto the throttle there is also a guiding means which is oriented in thedirection of the pilot chamber for the fluid stream such that the fluidstream guided in the connecting channel is deflected at least partly inthe direction of the valve part by the latter, the fluid stream which isdirected at the valve part of the pilot valve can be deflected and/orcan be atomized such that the jet forces no longer directly strike theclosing element of the pilot control, so that neutral dynamic effects onthe pilot control can be avoided and malfunctions can be reliablyprecluded in any valve state.

In one preferred embodiment of the valve as claimed in the invention,the throttle is designed as an orifice, the guiding means having atleast one atomizer part and/or deflector part. Furthermore provision ispreferably made such that the atomizer part is formed from individualatomizer nozzles and the deflection part is formed from at least onedeflection channel which assumes a definable oblique position relativeto the connecting channel. The fluid stream supplied by way of theconnecting channel and the orifice can be extremely finely dispersed inthe direction of the valve part of the pilot valve by way of theatomizer nozzles, so that the indicated jet forces on the valve part arethus appreciably reduced. Additionally or as an alternative, afluid-carrying deflection channel in the oblique position furthermorecan route the fluid stream as a helical guide in the direction of thepilot chamber, so that in this way the jet forces only come intoindirect contact with the valve part of the pilot valve.

In another preferred embodiment of the valve as claimed in theinvention, the throttle, especially in the form of an orifice, and theguiding means are two components which separately from one another canbe fixed in the connecting channel. It is possible to replace theguiding means for fluid jet guidance by another guiding means in orderin this way to be able to optimally adapt the valve to different pumppressure ranges (primary pressures). Preferably the guiding means, inparticular with the respective atomizer part and/or the respectivedeflection part is provided with another throttle, especially in theform of another orifice, so that the guiding means forms a so-calleddiffusion orifice, and the diffusor portion can be regarded inmathematical terms as a part of the flow channel with a flow crosssection which gradually widens so that the flow which takes place fromthe narrow to the wide cross section undergoes a reduction in speed witha simultaneous pressure rise, i.e., the jet speed is converted intopressure, with respect to the indicated atomization or jet guidance thisnot leading to damaging pressure jets on the valve part itself, butrather significantly improving only the inflow conditions in the area ofthe pilot chamber of the pilot valve.

Other advantageous embodiments of the valve as claimed in the invention,especially proportional pressure control valves, are the subject matterof the other dependent claims.

The valve as claimed in the invention is detailed below using aproportional pressure control valve according to one embodiment as shownin the drawings, in which in diagrammatic form and not drawn to scale

FIG. 1 shows partly in a front view, partly in a longitudinal section,the proportional pressure control valve as claimed in the invention inthe operating or actuating position, the valve being connected as ascrew-in cartridge with its valve housing into a receiving housing withthe individual valve ports A, P and T;

FIG. 2 shows in an enlarged cross section the pilot chamber with a partof the valve part and the combination of the throttle which is designedas an orifice with a diffusor orifice and upstream filter part, whichcombination is connected upstream in the direction of the fluid stream;

FIG. 3 shows partly in a perspective view, partly in a ghosted view, thediffusor orifice as shown in FIG. 2 viewed from the underside.

The valve as claimed in the invention in the form of a proportionalpressure control valve is shown in FIG. 1 in its basic structure. It hasa valve housing 10 which as a screw-in cartridge can be screwed into amachine part, for example in the form of a valve block 14 or the like,by way of a screw-in segment 12. For this connection the valve housing10 is provided on the outer circumferential side with the correspondingwashers 16, in addition to the pertinent receptacle for the sealingsystem. The valve housing 10 in the radial circumferential direction,and especially viewed in the direction of looking at FIG. 1, from top tobottom has a tank port T, a use port A and a pump port P for a hydraulicpump which is not shown in detail. Furthermore, a control piston 18 isguided so as to be movable in the longitudinal direction within thevalve housing 10 for optionally connecting the pump port P to the useport A and the use port A to the tank port T.

To establish a fluid-carrying connection between the pump port P and thepilot chamber 20 of a pilot valve which is designated as a whole as 22,the control piston 18 is provided with a connecting channel 24 which inthe longitudinal direction 26 of the entire valve extends in the middlethrough the control piston 18, the connecting channel 24 on its endwhich is the lower end viewed in the direction of looking at FIG. 1offset extending in the transverse direction and in this way leading tothe pump port P. Furthermore, the indicated pilot valve 22 can beactuated by way of a magnetic system, in particular one in the form of aproportional magnetic system, designated as a whole as 28. Thesemagnetic systems 28 generally have a coil winding (not shown) which canbe supplied with current, the magnetic system 28 having a plug connectorpart 30 for this purpose. When current is supplied to the proportionalmagnetic system 28 by way of its plug connector part 30, an actuatingplunger 32 is actuated by way of the coil winding which is not detailed,such that viewed in the direction of looking at FIG. 1 it has a downwarddirection of movement and thus keeps the actual pilot valve 22 shown inFIG. 1 in its closed position. This structure of the magnetic system 28in its mode of operation is known in the prior art so that it is notspecifically detailed here.

The connecting channel 24 has a throttle in the form of an orifice 34(compare also the enlargement in FIG. 2) in the direction of the pilotchamber 20 of the pilot valve 22. This orifice 34 constitutes a localflow resistance with a usually sudden cross sectional constriction inwhich the ratio of the length of the orifice to its diameter is selectedto be relatively small (for example approximately 1.5). The narrowestflow cross section is generally outside of the geometrical crosssectional constriction and since in these flow resistances the viscousfluid friction is very low, the volumetric flow is dependent on thepressure difference, and not on the viscosity of the fluid stream.

The orifice 34 in the fluid flow direction is connected downstream froma filter part 36, for example in the form of a protective screen, inorder to thus filter contaminants out of the fluid flow and to protectthe following orifice 34 against clogging by impurities. Following inthe fluid stream direction to the orifice 34, a fluid guiding means 38(compare FIG. 2) is connected downstream; it performs the function ofdeflecting the directed fluid stream which flows out of the orifice 34in the direction of the pilot chamber 20, so that it does not directlystrike the closing or valve part 40 of the pilot valve 22, whileotherwise in the prior art this led to malfunctions in certain valvestates. The guiding means 38 can be provided with atomizer nozzles whichensure that the added fluid flow is atomized in such a way that auniform homogeneous distribution of the fluid in the pilot chamber 20occurs, with the result that possible jet forces on the valve part 40are for the most part avoided. In addition or as an alternative to theindicated atomizer nozzles, the guiding means 38 can also be providedwith a deflection part designed as a deflection channel 42 illustratedin FIGS. 2 and 3 according to the exemplary embodiment shown. Thisdeflection channel 42 is tilted relative to the connecting channel 24and the longitudinal alignment 26 of the entire valve with a definableinclination, for example with an angle between 10° to 30°, with theresult that the fluid flow delivered by way of the connecting channel 24travels as a helical guide into the pilot chamber 20 and in this way,routed in a lateral path and guided radially around the tapering valvepart 40, the fluid stream comes into contact with the latter. The forceof the fluid stream on the valve part can thus also be reduced in eachof its operating positions. It has proven especially advantageous asshown in FIG. 3 in the fluid direction upstream from the inclineddeflection channel 42 to provide another throttle in the form of anotherorifice 44 which in terms of flow engineering then is particularlybeneficial when the proportional pressure control valve is to be usedfor high pump pressures (primary pressures). Furthermore it is possible,by replacing this component by a diffusor with a different orificediameter, to adapt the valve to different pump pressure ranges so thatin this way a plurality of requirement profiles can be accommodated withone valve design.

The pilot chamber 20 indicated in the foregoing is part of a valve seat46 mounted so as to be stationary in the valve housing 1, the valve seat46 being connected by way of a center channel 48 as a fluid-carryingcomponent of the pilot chamber 20 to the latter. This valve seat 46 canbe moved into sealing contact with the valve part 40 of the pilot valve20 as shown in FIG. 1, and the valve part 40 can be moved into itsclosed position shown in FIG. 1 spring-loaded in the direction of thepilot chamber 20. For contact with the actual valve seat 46 the valvepart 40 on its lower end which is the front end when viewed in thedirection of looking at FIG. 1 is provided with a tapering closing orvalve tip. The latter is in turn a one-piece component of a valve guideplate on which one respective compression spring 50 is mounted on bothsides. One compression spring 50 extends between the indicated valveguide plate and a flange-like widening on the bottom end of theactuating plunger 32, whereas the second compression spring 50, which isdesigned weaker in terms of its compression force than the firstcompression spring, extends with its two free ends between the valveguide plate and the top of the valve seat 46. For better guidance of theindicated compression springs 50, the valve guide plate as is shown inFIG. 1 can be provided with a cylindrical guidance or contact cap onboth sides.

For guidance of the valve guide plate, within the valve housing 10 thereis a guide part 52 which designed as a cylindrical sleeve is permanentlyconnected to the valve housing 10. Between the guide part 52 and theactual magnetic system 28 there is a screw-in part 54 thereof, withwhich the proportional magnetic system 28 can be attached to the valvehousing 10 and in such a way can be fixed. Furthermore, in the pertinentscrew-in part 54 the actuating plunger 32 with its flange-like wideningis guided on its one free end. Furthermore the guide part 52 with thestationary valve seat 46 adjoins a distribution space 56 which is madeas an annular channel. A fluid-carrying path 58 which is guided in thevalve housing 10 is permanently connected to this valve space 56 andalso discharges with its other free end into a connecting space 60adjoining the outside circumference of the valve housing 10 and theinside circumference of the valve block 14 into which the valve housing10 can be inserted and into which the tank port T in the valve block 14discharges.

A connection between the tank port T and the distribution space 56 istherefore obtained by way of the fluid-carrying path 58. Thefluid-carrying path 58 can be configured as shown in FIG. 1 from aplurality of individual channels which extend conically in the directionof the actuating plunger 32 and extend through the valve housing 10, atthe height of its screw-in segment 12. The respective end of theindicated individual channels oriented in the direction of the tank portT viewed in the direction of looking at FIG. 1 underneath the bottom endof the screw-in segment 12 exits to the outside or enters the connectingspace 60. Based on this structural design of the pilot valve 22, asdescribed in the foregoing, said pilot valve is accordingly designed asa proportional pressure relief valve.

As the figure furthermore shows, the control piston 18 with the valvehousing 10 on its end facing away from the pilot chamber 20 adjoins adamping chamber 62. In this damping chamber 62 there is an energystorage device, especially in the form of a compression spring 64, whichtries to move the control piston 18 in the direction of the pilotchamber 20. The damping chamber 62 is connected by way of a dampingorifice 66 located in the control piston 18 to an annulus 68 whichencloses the control piston 18 and which to the outside adjoins theinside of the valve housing 10. Depending on the longitudinal ordisplacement position of the control piston 18 in the valve housing 10,this annulus 66 optionally connects the tank port T to the use port A orthe use port A to the pump port P. The damping chamber 62 is enclosedboth by the inside of the valve housing 10 and on its one side adjoinsthe control piston 18, and on its opposite side adjoins a lift stop 70for the control piston 18. The actual lift stop 70 is formed by one freeside which faces the control piston 18 and otherwise this lift stop 70forms the termination of the valve housing 10 on its one side oppositethe valve block 14.

Since the structural design of the proportional pressure control valvehas now been described in its essential principles, for the sake ofbetter understanding the operating process will be described in greaterdetail below.

If the proportional magnetic system 28 remains without current supply,the hydraulic medium (oil) can flow from the pump port P to the tankport T. In this valve state the pilot valve 22 consequently must beopened and the control piston 19 is moved onto its upper stop againstthe lower side of the valve seat 46. In this operating position, the oilflows from the pump port P through the control piston 18, that is, byway of the connecting channel 24, and through the combination consistingof the filter part 36, orifice 34 and diffusor orifice consisting of theorifice 44 and deflection channel 42, and from there by way of theopened proportional pressure relief valve 22 of the pilot control to thetank T. The forces of the second compression spring 50 in conjunctionwith the pump pressure by way of the center channel 44 is sufficient toraise the valve guide plate with the valve part 40 against the action ofthe first compression spring 50 located over it. By way of the centerchannel 48 the hydraulic medium then travels into the distribution space56 and from there by way of the fluid-carrying path 58 into theconnecting space 60 which together with the tank port T leads to thetank. This volumetric flow can be defined as the pilot oil flow orleakage.

When the proportional magnetic system 28 is supplied with, current byupstream electronics (not shown), the closing or valve part 40 of thepilot valve 22 travels onto its seat edge of the valve seat 46 and inthe process interrupts the volumetric flow between the pump port P andthe tank port T. The pilot chamber 20 then fills up with the hydraulicmedium, as a result of which the pressure into this chamber rises. Thisprevailing pressure acts on the top front side of the control piston 18and moves it in the direction of the lower lift stop 70 against thecompressing third compression spring 64. The pressure in the pilotchamber then corresponds to the adjusted pressure.

When the pressure in the damping chamber 62 is less than the pressure inthe pilot chamber 20, the control piston assumes a position in which theconsumer port A is connected to the pump port P. The pressure on the useport A is signaled by way of the damping orifice to the damping chamber62 and there acts on the front side of the control piston 18 as acounterforce to the pressure level in the pilot chamber 20. When thepressure in the damping chamber 62 has reached the controlled pressure,the control piston 18 is moved so that the connection between the pumpport P and the consumer port A is throttled. The control piston 18shifts into a position in which the two force levels are in equilibriumwith one another and in this way define an opening window between thepump port P and the use port A. Accordingly, a pressure is generated onthe consumer port A which is directly related to the electrical controlsignal of the magnetic system 28. By adjusting the defined secondarypressure, a volume of oil is continuously pushed back and forth by wayof the damping orifice 66 between the damping chamber 62 and theconsumer port A, with the result that the control process is damped, inorder in this way to prevent disruptive vibrations during thisadjustment process.

In that, in the solution as claimed in the invention with the pilotvalve 22 opened, it clears the fluid-carrying path which is routed inpart in the valve housing between the connecting channel 24 and the tankport T which is connected at the same time to the consumer port A tocarry fluid, a valve is formed which can be completely relieved in thisway with the result that when the electronic control signal on themagnetic system 28 is omitted, the pressure which is controlled by wayof the control piston 18 on the consumer port A reliably assumes apressure value of 0 bar. Since the solution as claimed in the inventionthus omits returning the control piston (main stage) with a tensionedcompression spring to its end position corresponding to the knownsolutions, it is ensured that especially in an application for hydraulicclutches they can be completely relieved, so that the clutch or platestacks which otherwise are engaging are reliably detached from oneanother and thus release the clutch connection.

In the de-energized state, oil can flow from the pump port P to the tankport T. In this valve state the pilot valve 22 is opened and the controlpiston 18 has moved to its upper stop as is shown in FIG. 1. In thisstate the oil flows from the pump port P through the control piston 18through the filter orifice combination with the downstream diffusororifice 42, 44, by way of the opened proportional pressure relief valveof the pilot control to the tank T. This volumetric flow can be definedas a pilot oil flow or leakage. The diffusor orifice 42, 44, is used toatomize and deflect the directed oil jet which is flowing out of theorifice 34 such a distance that the jet forces generated by the fluidstream do not directly strike the closing element 40 of the pilotcontrol so that in such a way neutral dynamic effects on the pilotcontrol are reliably prevented, as well as any resulting malfunctions incertain valve states.

By the possibility of replacement of this component 42, 44 by a diffusorwith a different orifice diameter (not shown), the valve can beoptimally adapted to different pump pressure ranges (primary pressures)so that with a valve housing and the basically identical valve structurea plurality of applications can be accommodated. As is furthermore shownby FIG. 3, the fluid guiding means 38 is penetrated on its bottom by atransversely extending slotted guide 72, which is used for engagement ofa screwdriver which is not shown in order in such a way to fix the fluidguiding means 38 within a screw-in segment in the control piston. Inthis way the installation of the otherwise cylindrical component intothe control piston 18 can be greatly simplified. With the dampingorifice 66 an adaptation to different applications is possible by meansof the choice of the orifice diameter.

1. Valve, especially a proportional pressure control valve forcontrolling fluid flows, having a valve housing (10) which has at leastthree fluid-carrying ports, especially in the form of a pump port (P), ause port (A) and a tank port (T), within the valve housing (10) foroptional connection of the pump port (P) to the use port (A), and of theuse port (A) to the tank port (T), a control piston (18) being guided soas to be movable in the longitudinal direction which control piston isprovided with a connecting channel (24) for producing a fluid-carryingconnection between at least one of the ports (P) and the pilot chamber(20) of the pilot valve (22), the valve part (40) of the pilot valve(22) being guided so as to be movable in the longitudinal direction inthe pilot chamber (20), and the connecting channel (24) having athrottle in the direction of the pilot chamber (20) of the pilot valve(22) with its valve part (40), characterized in that in addition to thethrottle there is also a guiding means (38) which is oriented in thedirection of the pilot chamber (20) for the fluid stream so that thefluid stream guided in the connecting channel (24) is deflected at leastpartly in the direction of the valve part (40) by the latter.
 2. Thevalve as claimed in claim 1, wherein the throttle is designed as anorifice (34) and wherein the guiding means (38) has at least oneatomizer part and/or deflector part.
 3. The valve as claimed in claim 1,wherein the atomizer part is formed from individual atomizer nozzles andthe deflection part is formed from at least one deflection channel (42)which assumes a definable oblique position relative to the connectingchannel (24).
 4. The valve as claimed in claim 1, wherein the throttle,especially in the form of an orifice (34), and the guiding means (38)are two components which separately from one another can be fixed in theconnecting channel (24).
 5. The valve as claimed in claim 1, wherein thethrottle, especially in the form of an orifice (34), has a filter part(36) for the fluid stream on its side opposite the guiding means (38).6. The valve as claimed in claim 2, wherein the atomizer part and/or thedeflection part are provided with another throttle, especially in theform of another orifice (44).
 7. The valve as claimed in claim 1,wherein the pilot valve (22) can be actuated by a magnetic system (28),especially a proportional magnetic system.
 8. The valve as claimed inclaim 1, wherein the pilot chamber (20) is part of a valve seat (46)which is mounted so as to be stationary in the valve housing (10), whichvalve seat is connected to the pilot chamber (20) to carry fluid, andwhich can be moved into sealing contact with the valve part (40) of thepilot valve (22) which can be moved into its closed positionspring-loaded in the direction of the pilot chamber (20).
 9. The valveas claimed in claim 1, wherein all fluid-carrying ports (A, P, T) extendthrough the valve housing (10) in the radial direction.